Aerophone.



L. DE FOREST.

AEROPHONE.

APPLICATION FILED DEG. 11. 1905.

PATENTED NOV. 13, 1906.

UNITED STATES PATENT OFFICE;

LEE DE FOREST, OF NEW YORK, N. Y.

AEROPHONE.

Specification of Letters; Patent.

Patented Nov. 13, 1906..

Application filed Deoeliibar'll, 1906. Serial No. 291,222,

T0 on whom it may concern.-

Be it'known that I, LEE DE FoREsT, a citizen of the United States, and a resident of New York, in the county of New York .and State of New York, have invented a new and useful Improvement in Aerophones, of which the following is a s ecification.

My invention re atesto wireless-telephone systems for transmitting and receiving vocal or other sounds, including articulate speech,

by electromagnetic Waves.

The object of my invention is to produce a wireless telephone or aerophone in which a resistance device-is varied by and in accordance with the air-vibrations accompanying:-

having reference to the drawings which accompany and form a part of this specifica tion and which illustrate conventionally several devices and systems of circuits whereby my invention may-becarried into efl ect.

In the drawings, Figures 1, 2, and 3 are diagrams of aerophone transmitting systems.

I In Figs. 1, 2, and 3, G is a high-frequency alternating-current generator. producing at least seven hundred and fifty cycles per second and preferably the frequency of said gen-' erator should be as high as can conveniently and commercially be produced.

In Fi s. 1 and 3' the generatorGenergizes the oscil ating circuitC S L directly, although as shown in Fig. 2, the'transform'er I maybe interposed between said circuit and generator for appropriately varying the difference of potential impressed upon the condenser C by the generator. By meansof the adjustable connections of the oscillating circuit and antenna A with the inductance L the natural periods of said antenna and circuit may be brought into agreement.

The element shown in the several figures as K K K represents a resistance device of any suitable character which is adapted to be controlled by the vibrations of the air accompanying vocal or other sounds, including articulate speech.

In Fig. 1,

' able salts.

K is represented as a carbon mi-' crophone, preferably of the kind used in circuits carrying currents of amplitudes large compared to the amplitudes of the currents which are modified-by the usual granular car bon transmitter in ordinary wire tele hony. In Fig. 2, Kf is a flame made more con noting by the addition of sodium salts or other suite The variable-resistance devices ma be placed, as shown in Figs. 1,2, an 3, at

points in the system near the earth connection, because at such points the current in the system is near its maximum. value and the potential is near its minimum value. Accordingly, the said resistance devices are less liable to be injured or rendered inoperative by having excessive potentials impressed upon their terminals and are enabled to produce a far greater variation in'the amplitude of the currents in the antenna, and hence in the amplitude of the radiated waves by slight changes in resistance, than if they were locatedfbetween the inductance L and the top of the antenna. In other words, I do not limit myself to any particular type of variable-resistance transmitter, but consider any suitable transmitter operatively associated with the system as set forth in theclaims within the scope of my invention when used to varyl the amplitude of electrical oscillations roduced by a continuouslyoperating train ofsparkshaving "a spark-gap frequency higher than the frequency of the more essential vibrations accom anyin speech-as forexample, fifteen pulsations per second.

With all the variable-resistance devices K any suitable sound amplifying and concentrating devicemaybeused-such, for example, as the megaphone M (shown inv Figs. 2 and 3) or the well-known compressed-air device F, (shown in Fig. 3,) in which the diaphragm V of the megaphone operates on a reducing-valve to vary the flow of air from the tank F through the nozzle G In Fig. 3, K is a spark-gap.

est

undre The operation is as follows: In Figs. 1, 2,

and 3 the generators G charge the condensers C a sufficient number of times per second to create in the oscillating circuits 8- C L electrical oscillations having a spark frequency higher than the more essential frequencies whichv make up the complex voice-waves, and said oscillations result in the radiation from the antenna of electromagnetic waves having similar spark frequency. The electromagnetic waves develop oscillations in a receiving-antenna, thereby producing acurrent varying at a rate equalto the sparkfrequency of the transmitted waves. The effect of'said varying current on the telephone-receiver de pends, of course, upon the rate of its variation. If desired,'this rate may be made to exceed the limit of response of the telephonediaphragm; but such rapid variation is not necessary, 'all that is necessary being, as in.

the case of the well-known Gibboney or Hutin lfieblanc' alt'emating ourrent systems of telephony, that the rate of current variation in telephone-circuit be higher than the most important frequencies occurring in telephonic transmission, inwhich case the telephone will produce a note having the pitch equal to the spark frequency employed at the transmitting station'. In eithercase any variation in the amplitude of the currents inthe local telephone-circuit will'produce a cor responding variation in the sound emitted by the tele hone and therefore if by any of the variab 'e-resistance' transmitters shown herein or by any other means the amplitude of the transmitted waves be modified in a manner corresponding to the voice waves ratus, and accordingly it will be obvious t atmany other devices and systems may be devised for varying by and in accordance with speech-Waves the amplitude of continuously transmitted trains of waves-having a spark gapfrequency higher than the more essential frequencies accompanying speech, and therefore I do not wish to' limit my invention to'theparticular embodiments thereof herein shown and described.

\ seems I I claim a 1.- The-method of transmitting speech by electromagnetic ether-waves, which consists in developing in an antenna electrical oscillations having a spark frequencyihigher than i the more essential frequencies accom anying speech, modifyin said oscillations etween the'point at which energy is supplied to the antenna and the earth connection thereof by and in accordance with speech-waves, and converting the modified oscillations into electroradiant energy.

2. The method of: transmitting vocal or other sounds by electromagnetic ether-waves which consists in developing in an antenna electrical oscillations having a sparkfrequency higher than the more essential frequencies accompanying the sounds to be transmitted, modifyingsaid oscillations at a point below that at which the energy issupplied to the antenna in accordance'wit'h said sounds and convertin the oscillations so modified into elec trora ant energy. a

3. The method of transmitting speech by electromagnetic ether-wa ves which consists in developing: electrical oscillations having a spark frequency higher than the more essential frequencies accompanying speech, translating the energy of said oscillations to a transmitting-antenna, modifying the oscillations in said antenna at a point below that at which the energy is supplied to the antenna in accordance with'the vibrations of the air accompanying speech and converting the modified oscillations into electroradiant energy.

- In testimony whereof I have hereunto sub scribed my name this 7th day of December, 1905. LEE DE FOREST.

Witnesses: I

LESTER Tnsrur,

mrr Fn'nnswon'mz 

